Why are there 21 serrations on beer cown caps?

How many serrations are there on a beer bottle cap? This must have stumped a lot of people. To tell you exactly, all beer you see every day, whether it’s a large bottle or a small bottle, has 21 serrations on the lid. So why are there 21 serrations on the cap?

As early as the end of the 19th century, William Pate invented and patented the 24-tooth bottle cap. The inside is also padded with a piece of paper to prevent the drink from coming into contact with the metal, largely based on Pete’s finding that this number of teeth is best for bottle sealing. As the industry standard, the 24-tooth cap was in use until around the 1930s.

With the process of industrialization, the original method of manual capping has become industrial capping. The 24-tooth caps were first put on the bottles one by one with a foot press. After the automatic machine appeared, the bottle cap was put into a hose and installed automatically, but during use, it was found that the 24-tooth bottle cap could easily block the hose of the automatic filling machine. If it was changed to 23-tooth, this situation would not occur. , and finally gradually standardized to 21 teeth.

Back to the topic, why is 21 teeth the most suitable?

Of course, this does not mean that if you want to reduce one, it is as simple as reducing one. It is the crystallization of people’s practice and wisdom to determine to maintain 21 teeth.
Beer contains a lot of carbon dioxide. There are two basic requirements for bottle caps. One is to have good sealing, and the other is to have a certain degree of bite, that is, the commonly known bottle cap must be firm. This means that the number of pleats on each bottle cap should be proportional to the contact area of the bottle mouth to ensure that the contact surface area of each pleat can be larger, and the wavy seal on the outside of the bottle cap can increase friction and facilitate convenience. On, 21 teeth is the best option for both requirements.

Another reason why the number of serrations on the bottle cap is 21 is related to the screwdriver. Beer contains a lot of gas if not turned on properly. If the air pressure inside is uneven, it is very easy to hurt people. After inventing a screwdriver suitable for opening bottle caps, and by constantly modifying the saw teeth, it is finally determined that when the bottle cap has 21 teeth, it is the easiest and safest to open, so, all you see today Beer bottle caps have 21 serrations.